The communication device can be understood as a device provided with appropriate communication and control capabilities for enabling use thereof for communication with other parties. The communication may comprise, for example, communication of voice, electronic mail (email), text messages, data, multimedia and so on. A communication device typically enables a user of the device to receive and transmit communications via a communications system and can thus be used for accessing various applications.
A communication system is a facility which facilitates the communication between two or more entities such as the communication devices, network entities and other nodes. An appropriate access system allows the communication device to access the communication system. An access to the communication system may be provided by means of a fixed line or wireless communication interface, or a combination of these.
Communication systems providing wireless access typically enable at least some mobility for the users thereof. Examples of these include cellular wireless communications systems where the access is provided by means of access entities called cells. Other examples of wireless access technologies include Wireless Local Area Networks (WLANs) and satellite based communication systems.
Generally, a communication device will incorporate one or more Integrated Circuits (IC). Integrated circuit process variations can cause the analog components of an integrated circuit to have different properties from chip to chip. Environmental conditions, such as temperature, operating voltages and aging, can also change the analog component properties. Additionally, some transceiver architectures may suffer from degraded performance that requires periodic compensation. An example of this is the direct conversion receiver DC (Direct Current) offset cancellation between bursts in a TDMA (Time Division Multiple Access) system. Radio Frequency (RF) designers need to take into account these process variations, environmental conditions and other degradation in performance. Accordingly, designs which have been proposed generally include calibration or compensation circuitry. For example, switchable capacitor matrices, adjustable biasing currents or the like may be provided.
The inventors have appreciated that the calibration required can be divided roughly into five different categories:
1. Foundry—ASIC (application specific integrated circuit)/module fabrication—calibrations required to compensate the integrated circuit itself.
2. Factory (communication device fabrication)—that is when the communication device incorporating the IC is manufactured.
3. Communication device start-up, for example when the communication device is used for the first time or switched on.
4. On-line—(idle mode), that is when the communication device is turned on but not actually being used.
5. Environmental—where the communication device is in an active mode, that is switched on and being used.
It is known to provide “one time” calibrations during fabrication of the communication device during testing. To facilitate this, radio frequency designers have provided custom logic to facilitate specific calibrations.
However, the inventors have appreciated that providing different calibration logic to deal with each different type of calibration makes it difficult to reuse the logic in different designs as it is much customized. Additionally, the customised logic for each of the different types of calibration takes up space on the IC area, which is undesirable.
The problem mentioned above is exacerbated when the communication device is provided with so called multi-radio capabilities. That is, the same communications device may be used for communication via a plurality of different wireless interfaces. Managing the calibration of multi-radio transceivers is complex since the same radio frequency hardware can be configured for a number of different radio systems.
It is an aim of one or more embodiments of the invention to address or at least mitigate one or more of the problems set out above.